Electrodeposition of molybdenumcobalt alloys



Patente cl Oct. 7, 1 947 UNITED STATES PATENT" mm j ELECTRODEPOSITI'ON-oF MOLYBDENUM- I COBALT ALLOYS Leonard F. Yntemm Waukegan, Ill.,'assignor' to President &- Board of Trustees of St. Louis University,St. Louis, Mo'.

No Drawing, Application April 24,1944; Serial No. 532,526

The invention relates to the electrocodeposition of an alloy ofmolybdenum and a metal of the class consisting of cobalt and iron fromaqueous solutions.

I have discovered that such alloys may be codeposited from aqueoussolutions when the molybdenum is present in the solution in thehexavalent form, when free alkali metal hydroxide is present and whenthere is an addition agent capable of holding the cobalt or iron insolution.

In preparing the electrolyte, the molybdenum is added to the water inthe form of the alkali metal salt, or, if desired, it may be added asmolybdic acid or its anhydride, in which case it is converted into themolybdate form by the free alkali hydroxide. It is essential that freealkali hydroxide be present in the electrolyte during theelectrodeposition and it is preferable that the electrolyte also containalkali metal carbonate. The cobalt or iron is added in the form of asalt such as sulfate, chloride, etc., but to maintain the same insolution it is necessary to add an organic compound having a hydroxylgroup and capable of forming complexes with the cobalt or iron. Examplesof such organic compounds are sugars, glycerine, glycols and tartaricacid. Inorganic compounds such as phosphates, sulfates and cyanides willnot function for this purpose. Preferably I use dextrose.

The electrolyte must be strongly alkaline and good deposits are obtainedfrom a solution containing 250 grams per liter of sodium hydroxide and80 grams per liter of sodium carbonate. The current density may bevaried from 0.03 ampere per square decimeter to 0.5 or higher. Depositsmay be obtained at room temperatures or at higher temperatures. I haveobtained satisfactory deposits on cathodes of copper and iron. Themolybdenum-cobalt plates are bright, very hard and adherent, and areresistant to tarnishing by the atmosphere and to the action of a 3%sodium chloride solution.

I have been unable to obtain alloys of molybdenum with nickel, zinc, tinor bismuth. While I do not wish to be limited to any particular theoryas to the operation of my process, it is my understanding that cobaltand iron function as they do because their hydroxides are slightlysoluble in strong alkalies. It is possible that the hydrogen, which isdischarged as atomic hydrogen along with the cobalt or ron and isdissolved in or is absorbed by them, reduces the molybdenum compounds tothe metal by a secondary reaction. This picture of the mechanism of thereaction is based on the facts that no molybdenum is 5 Claims. (01.204-43) deposited as metal unless cobalt or iron is present, that nickeldoes not function because its hydroxide is not soluble in the alkalinesolutions, and that iron functions better when in the ferric state,which should be more soluble in the strong alkali than the ferrous form.It is my understanding that atomic hydrogen does not dissolve as readilyin zinc, tin, and bismuth and therefore these metals do not function.

The following is an example of a suitable electrolyte for codepositionof an alloy of molybdenum and cobalt in accordance with my invention:

What I claim as my invention is:

1. The process for electrodepositing an alloy of molybdenum and a metalof the class consisting of cobalt and iron which consists in passing acurrent between an anode and the work to be plated as a cathode in anaqueous electrolyte consisting essentially of 10 to 30 grams per literof a hexavalent molybdate compound, 5 to 15 grams per liter of a solublecompound of a metal of the class consisting of cobalt and iron, to 300grams per liter of free alkali metal hydroxide and 10 to 30 grams perliter of an organic compound having a hydroxyl group of the classconsisting of sugars, glycerine, glycols and tartaric acid.

2. The process for electrocodepositing an alloy of molybdenum and cobaltwhich consists in passing a current between an anode and the work to beplated as a cathode in an aqueous electrolyte consisting essentially of10 to 30 grams per liter of a hexavalent molybdate compound, 5 to 15grams per liter of a soluble cobalt compound, 100 to 300 grams per literof free alkali metal hy- .droxide, and 10 to 30 grams per liter f anorganic compound having a hydroxyl group of the class consisting ofsugars, glycerine, glycols and tartaric acid.

3. The process for electrocodepositing an alloy of molybdenum and cobaltwhich consists in passing a current between an anode and the work to beplated as a cathode in an aqueous electrolyte consisting essentially ofalkali metal molybdate from 10 to 30 grams per liter, cobalt sulfate 5to 15 grams per liter, alkali metal hydroxide 100 to 300 grams perliter, alkali metal carbonate 40 to 120 grams per liter and an organicSodium molybdate grams Cobalt sulfate do 1 Sodium hydroxide do 250Sodium carbonate do 80' Dextrose do to 30 5. The process forelectrocodepositing an alloy of molybdenum and cobalt which consistsln'pa ss ing a current between an anode and the work to V be plated as acathode in an aqueous electrolyte consisting essentially of alkali metalmolybdate from 10 to grams per liter, cobalt sulfate 5 to 15 grams perliter, alkali metal hydroxide to 300 grams per liter, alkali metalcarbonate 40 to grams per liter, and dextrose 10 td 30;

grams per liter. 7 a I LEONARD F.- YNTEMA.

REFERENCES cI'rEn Water liters The following references are of record inthe a file of this patent: UNITED STATES PATENTS Number Name Date1,885,700 V Fink Nov. 1, 1932 FOREIGN PATENTS Number Country Date 1,183Great Britain 1852 582,528

Germany May 22, 1934

